#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int slalsd_(char *uplo, integer *smlsiz, integer *n, integer 
	*nrhs, real *d__, real *e, real *b, integer *ldb, real *rcond, 
	integer *rank, real *work, integer *iwork, integer *info  	)
{
/*  -- LAPACK routine (version 3.1) --   
       Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..   
       November 2006   


    Purpose   
    =======   

    SLALSD uses the singular value decomposition of A to solve the least   
    squares problem of finding X to minimize the Euclidean norm of each   
    column of A*X-B, where A is N-by-N upper bidiagonal, and X and B   
    are N-by-NRHS. The solution X overwrites B.   

    The singular values of A smaller than RCOND times the largest   
    singular value are treated as zero in solving the least squares   
    problem; in this case a minimum norm solution is returned.   
    The actual singular values are returned in D in ascending order.   

    This code makes very mild assumptions about floating point   
    arithmetic. It will work on machines with a guard digit in   
    add/subtract, or on those binary machines without guard digits   
    which subtract like the Cray XMP, Cray YMP, Cray C 90, or Cray 2.   
    It could conceivably fail on hexadecimal or decimal machines   
    without guard digits, but we know of none.   

    Arguments   
    =========   

    UPLO   (input) CHARACTER*1   
           = 'U': D and E define an upper bidiagonal matrix.   
           = 'L': D and E define a  lower bidiagonal matrix.   

    SMLSIZ (input) INTEGER   
           The maximum size of the subproblems at the bottom of the   
           computation tree.   

    N      (input) INTEGER   
           The dimension of the  bidiagonal matrix.  N >= 0.   

    NRHS   (input) INTEGER   
           The number of columns of B. NRHS must be at least 1.   

    D      (input/output) REAL array, dimension (N)   
           On entry D contains the main diagonal of the bidiagonal   
           matrix. On exit, if INFO = 0, D contains its singular values.   

    E      (input/output) REAL array, dimension (N-1)   
           Contains the super-diagonal entries of the bidiagonal matrix.   
           On exit, E has been destroyed.   

    B      (input/output) REAL array, dimension (LDB,NRHS)   
           On input, B contains the right hand sides of the least   
           squares problem. On output, B contains the solution X.   

    LDB    (input) INTEGER   
           The leading dimension of B in the calling subprogram.   
           LDB must be at least max(1,N).   

    RCOND  (input) REAL   
           The singular values of A less than or equal to RCOND times   
           the largest singular value are treated as zero in solving   
           the least squares problem. If RCOND is negative,   
           machine precision is used instead.   
           For example, if diag(S)*X=B were the least squares problem,   
           where diag(S) is a diagonal matrix of singular values, the   
           solution would be X(i) = B(i) / S(i) if S(i) is greater than   
           RCOND*max(S), and X(i) = 0 if S(i) is less than or equal to   
           RCOND*max(S).   

    RANK   (output) INTEGER   
           The number of singular values of A greater than RCOND times   
           the largest singular value.   

    WORK   (workspace) REAL array, dimension at least   
           (9*N + 2*N*SMLSIZ + 8*N*NLVL + N*NRHS + (SMLSIZ+1)**2),   
           where NLVL = max(0, INT(log_2 (N/(SMLSIZ+1))) + 1).   

    IWORK  (workspace) INTEGER array, dimension at least   
           (3*N*NLVL + 11*N)   

    INFO   (output) INTEGER   
           = 0:  successful exit.   
           < 0:  if INFO = -i, the i-th argument had an illegal value.   
           > 0:  The algorithm failed to compute an singular value while   
                 working on the submatrix lying in rows and columns   
                 INFO/(N+1) through MOD(INFO,N+1).   

    Further Details   
    ===============   

    Based on contributions by   
       Ming Gu and Ren-Cang Li, Computer Science Division, University of   
         California at Berkeley, USA   
       Osni Marques, LBNL/NERSC, USA   

    =====================================================================   


       Test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    static real c_b6 = 0.f;
    static integer c__0 = 0;
    static real c_b11 = 1.f;
    
    /* System generated locals */
    integer b_dim1, b_offset, i__1, i__2;
    real r__1;
    /* Builtin functions */
    double log(doublereal), r_sign(real *, real *);
    /* Local variables */
    static integer c__, i__, j, k;
    static real r__;
    static integer s, u, z__;
    static real cs;
    static integer bx;
    static real sn;
    static integer st, vt, nm1, st1;
    static real eps;
    static integer iwk;
    static real tol;
    static integer difl, difr;
    static real rcnd;
    static integer perm, nsub, nlvl, sqre, bxst;
    extern /* Subroutine */ int srot_(integer *, real *, integer *, real *, 
	    integer *, real *, real *), sgemm_(char *, char *, integer *, 
	    integer *, integer *, real *, real *, integer *, real *, integer *
, real *, real *, integer *);
    static integer poles, sizei, nsize;
    extern /* Subroutine */ int scopy_(integer *, real *, integer *, real *, 
	    integer *);
    static integer nwork, icmpq1, icmpq2;
    extern doublereal slamch_(char *);
    extern /* Subroutine */ int slasda_(integer *, integer *, integer *, 
	    integer *, real *, real *, real *, integer *, real *, integer *, 
	    real *, real *, real *, real *, integer *, integer *, integer *, 
	    integer *, real *, real *, real *, real *, integer *, integer *), 
	    xerbla_(char *, integer *), slalsa_(integer *, integer *, 
	    integer *, integer *, real *, integer *, real *, integer *, real *
	    , integer *, real *, integer *, real *, real *, real *, real *, 
	    integer *, integer *, integer *, integer *, real *, real *, real *
	    , real *, integer *, integer *), slascl_(char *, integer *, 
	    integer *, real *, real *, integer *, integer *, real *, integer *
	    , integer *);
    static integer givcol;
    extern integer isamax_(integer *, real *, integer *);
    extern /* Subroutine */ int slasdq_(char *, integer *, integer *, integer 
	    *, integer *, integer *, real *, real *, real *, integer *, real *
	    , integer *, real *, integer *, real *, integer *), 
	    slacpy_(char *, integer *, integer *, real *, integer *, real *, 
	    integer *), slartg_(real *, real *, real *, real *, real * 	    ), slaset_(char *, integer *, integer *, real *, real *, real *, 
	    integer *);
    static real orgnrm;
    static integer givnum;
    extern doublereal slanst_(char *, integer *, real *, real *);
    extern /* Subroutine */ int slasrt_(char *, integer *, real *, integer *);
    static integer givptr, smlszp;


    --d__;
    --e;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;

    if (*n < 0) {
	*info = -3;
    } else if (*nrhs < 1) {
	*info = -4;
    } else if (*ldb < 1 || *ldb < *n) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SLALSD", &i__1);
	return 0;
    }

    eps = slamch_("Epsilon");

/*     Set up the tolerance. */

    if (*rcond <= 0.f || *rcond >= 1.f) {
	rcnd = eps;
    } else {
	rcnd = *rcond;
    }

    *rank = 0;

/*     Quick return if possible. */

    if (*n == 0) {
	return 0;
    } else if (*n == 1) {
	if (d__[1] == 0.f) {
	    slaset_("A", &c__1, nrhs, &c_b6, &c_b6, &b[b_offset], ldb);
	} else {
	    *rank = 1;
	    slascl_("G", &c__0, &c__0, &d__[1], &c_b11, &c__1, nrhs, &b[
		    b_offset], ldb, info);
	    d__[1] = dabs(d__[1]);
	}
	return 0;
    }

/*     Rotate the matrix if it is lower bidiagonal. */

    if (*(unsigned char *)uplo == 'L') {
	i__1 = *n - 1;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    slartg_(&d__[i__], &e[i__], &cs, &sn, &r__);
	    d__[i__] = r__;
	    e[i__] = sn * d__[i__ + 1];
	    d__[i__ + 1] = cs * d__[i__ + 1];
	    if (*nrhs == 1) {
		srot_(&c__1, &b[i__ + b_dim1], &c__1, &b[i__ + 1 + b_dim1], &
			c__1, &cs, &sn);
	    } else {
		work[(i__ << 1) - 1] = cs;
		work[i__ * 2] = sn;
	    }
/* L10: */
	}
	if (*nrhs > 1) {
	    i__1 = *nrhs;
	    for (i__ = 1; i__ <= i__1; ++i__) {
		i__2 = *n - 1;
		for (j = 1; j <= i__2; ++j) {
		    cs = work[(j << 1) - 1];
		    sn = work[j * 2];
		    srot_(&c__1, &b[j + i__ * b_dim1], &c__1, &b[j + 1 + i__ *
			     b_dim1], &c__1, &cs, &sn);
/* L20: */
		}
/* L30: */
	    }
	}
    }

/*     Scale. */

    nm1 = *n - 1;
    orgnrm = slanst_("M", n, &d__[1], &e[1]);
    if (orgnrm == 0.f) {
	slaset_("A", n, nrhs, &c_b6, &c_b6, &b[b_offset], ldb);
	return 0;
    }

    slascl_("G", &c__0, &c__0, &orgnrm, &c_b11, n, &c__1, &d__[1], n, info);
    slascl_("G", &c__0, &c__0, &orgnrm, &c_b11, &nm1, &c__1, &e[1], &nm1, 
	    info);

/*     If N is smaller than the minimum divide size SMLSIZ, then solve   
       the problem with another solver. */

    if (*n <= *smlsiz) {
	nwork = *n * *n + 1;
	slaset_("A", n, n, &c_b6, &c_b11, &work[1], n);
	slasdq_("U", &c__0, n, n, &c__0, nrhs, &d__[1], &e[1], &work[1], n, &
		work[1], n, &b[b_offset], ldb, &work[nwork], info);
	if (*info != 0) {
	    return 0;
	}
	tol = rcnd * (r__1 = d__[isamax_(n, &d__[1], &c__1)], dabs(r__1));
	i__1 = *n;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    if (d__[i__] <= tol) {
		slaset_("A", &c__1, nrhs, &c_b6, &c_b6, &b[i__ + b_dim1], ldb);
	    } else {
		slascl_("G", &c__0, &c__0, &d__[i__], &c_b11, &c__1, nrhs, &b[
			i__ + b_dim1], ldb, info);
		++(*rank);
	    }
/* L40: */
	}
	sgemm_("T", "N", n, nrhs, n, &c_b11, &work[1], n, &b[b_offset], ldb, &
		c_b6, &work[nwork], n);
	slacpy_("A", n, nrhs, &work[nwork], n, &b[b_offset], ldb);

/*        Unscale. */

	slascl_("G", &c__0, &c__0, &c_b11, &orgnrm, n, &c__1, &d__[1], n, 
		info);
	slasrt_("D", n, &d__[1], info);
	slascl_("G", &c__0, &c__0, &orgnrm, &c_b11, n, nrhs, &b[b_offset], 
		ldb, info);

	return 0;
    }

/*     Book-keeping and setting up some constants. */

    nlvl = (integer) (log((real) (*n) / (real) (*smlsiz + 1)) / log(2.f)) + 1;

    smlszp = *smlsiz + 1;

    u = 1;
    vt = *smlsiz * *n + 1;
    difl = vt + smlszp * *n;
    difr = difl + nlvl * *n;
    z__ = difr + (nlvl * *n << 1);
    c__ = z__ + nlvl * *n;
    s = c__ + *n;
    poles = s + *n;
    givnum = poles + (nlvl << 1) * *n;
    bx = givnum + (nlvl << 1) * *n;
    nwork = bx + *n * *nrhs;

    sizei = *n + 1;
    k = sizei + *n;
    givptr = k + *n;
    perm = givptr + *n;
    givcol = perm + nlvl * *n;
    iwk = givcol + (nlvl * *n << 1);

    st = 1;
    sqre = 0;
    icmpq1 = 1;
    icmpq2 = 0;
    nsub = 0;

    i__1 = *n;
    for (i__ = 1; i__ <= i__1; ++i__) {
	if ((r__1 = d__[i__], dabs(r__1)) < eps) {
	    d__[i__] = r_sign(&eps, &d__[i__]);
	}
/* L50: */
    }

    i__1 = nm1;
    for (i__ = 1; i__ <= i__1; ++i__) {
	if ((r__1 = e[i__], dabs(r__1)) < eps || i__ == nm1) {
	    ++nsub;
	    iwork[nsub] = st;

/*           Subproblem found. First determine its size and then   
             apply divide and conquer on it. */

	    if (i__ < nm1) {

/*              A subproblem with E(I) small for I < NM1. */

		nsize = i__ - st + 1;
		iwork[sizei + nsub - 1] = nsize;
	    } else if ((r__1 = e[i__], dabs(r__1)) >= eps) {

/*              A subproblem with E(NM1) not too small but I = NM1. */

		nsize = *n - st + 1;
		iwork[sizei + nsub - 1] = nsize;
	    } else {

/*              A subproblem with E(NM1) small. This implies an   
                1-by-1 subproblem at D(N), which is not solved   
                explicitly. */

		nsize = i__ - st + 1;
		iwork[sizei + nsub - 1] = nsize;
		++nsub;
		iwork[nsub] = *n;
		iwork[sizei + nsub - 1] = 1;
		scopy_(nrhs, &b[*n + b_dim1], ldb, &work[bx + nm1], n);
	    }
	    st1 = st - 1;
	    if (nsize == 1) {

/*              This is a 1-by-1 subproblem and is not solved   
                explicitly. */

		scopy_(nrhs, &b[st + b_dim1], ldb, &work[bx + st1], n);
	    } else if (nsize <= *smlsiz) {

/*              This is a small subproblem and is solved by SLASDQ. */

		slaset_("A", &nsize, &nsize, &c_b6, &c_b11, &work[vt + st1], 
			n);
		slasdq_("U", &c__0, &nsize, &nsize, &c__0, nrhs, &d__[st], &e[
			st], &work[vt + st1], n, &work[nwork], n, &b[st + 
			b_dim1], ldb, &work[nwork], info);
		if (*info != 0) {
		    return 0;
		}
		slacpy_("A", &nsize, nrhs, &b[st + b_dim1], ldb, &work[bx + 
			st1], n);
	    } else {

/*              A large problem. Solve it using divide and conquer. */

		slasda_(&icmpq1, smlsiz, &nsize, &sqre, &d__[st], &e[st], &
			work[u + st1], n, &work[vt + st1], &iwork[k + st1], &
			work[difl + st1], &work[difr + st1], &work[z__ + st1],
			 &work[poles + st1], &iwork[givptr + st1], &iwork[
			givcol + st1], n, &iwork[perm + st1], &work[givnum + 
			st1], &work[c__ + st1], &work[s + st1], &work[nwork], 
			&iwork[iwk], info);
		if (*info != 0) {
		    return 0;
		}
		bxst = bx + st1;
		slalsa_(&icmpq2, smlsiz, &nsize, nrhs, &b[st + b_dim1], ldb, &
			work[bxst], n, &work[u + st1], n, &work[vt + st1], &
			iwork[k + st1], &work[difl + st1], &work[difr + st1], 
			&work[z__ + st1], &work[poles + st1], &iwork[givptr + 
			st1], &iwork[givcol + st1], n, &iwork[perm + st1], &
			work[givnum + st1], &work[c__ + st1], &work[s + st1], 
			&work[nwork], &iwork[iwk], info);
		if (*info != 0) {
		    return 0;
		}
	    }
	    st = i__ + 1;
	}
/* L60: */
    }

/*     Apply the singular values and treat the tiny ones as zero. */

    tol = rcnd * (r__1 = d__[isamax_(n, &d__[1], &c__1)], dabs(r__1));

    i__1 = *n;
    for (i__ = 1; i__ <= i__1; ++i__) {

/*        Some of the elements in D can be negative because 1-by-1   
          subproblems were not solved explicitly. */

	if ((r__1 = d__[i__], dabs(r__1)) <= tol) {
	    slaset_("A", &c__1, nrhs, &c_b6, &c_b6, &work[bx + i__ - 1], n);
	} else {
	    ++(*rank);
	    slascl_("G", &c__0, &c__0, &d__[i__], &c_b11, &c__1, nrhs, &work[
		    bx + i__ - 1], n, info);
	}
	d__[i__] = (r__1 = d__[i__], dabs(r__1));
/* L70: */
    }

/*     Now apply back the right singular vectors. */

    icmpq2 = 1;
    i__1 = nsub;
    for (i__ = 1; i__ <= i__1; ++i__) {
	st = iwork[i__];
	st1 = st - 1;
	nsize = iwork[sizei + i__ - 1];
	bxst = bx + st1;
	if (nsize == 1) {
	    scopy_(nrhs, &work[bxst], n, &b[st + b_dim1], ldb);
	} else if (nsize <= *smlsiz) {
	    sgemm_("T", "N", &nsize, nrhs, &nsize, &c_b11, &work[vt + st1], n, 
		     &work[bxst], n, &c_b6, &b[st + b_dim1], ldb);
	} else {
	    slalsa_(&icmpq2, smlsiz, &nsize, nrhs, &work[bxst], n, &b[st + 
		    b_dim1], ldb, &work[u + st1], n, &work[vt + st1], &iwork[
		    k + st1], &work[difl + st1], &work[difr + st1], &work[z__ 
		    + st1], &work[poles + st1], &iwork[givptr + st1], &iwork[
		    givcol + st1], n, &iwork[perm + st1], &work[givnum + st1],
		     &work[c__ + st1], &work[s + st1], &work[nwork], &iwork[
		    iwk], info);
	    if (*info != 0) {
		return 0;
	    }
	}
/* L80: */
    }

/*     Unscale and sort the singular values. */

    slascl_("G", &c__0, &c__0, &c_b11, &orgnrm, n, &c__1, &d__[1], n, info);
    slasrt_("D", n, &d__[1], info);
    slascl_("G", &c__0, &c__0, &orgnrm, &c_b11, n, nrhs, &b[b_offset], ldb, 
	    info);

    return 0;

/*     End of SLALSD */

} /* slalsd_ */